Most proteins strongly absorb light at 280nm. If this is true, then we should theoretically be able to measure the protein concentration of a cell lysate simply by measuring OD280. In practice, this will not work; that is to say, measuring OD280 will not give an accurate measurement of the actual protein concentration of the cell lysate. Why? What other major cell components absorb light at 260nm at peak and sianificantlv at 280nm ?.